Check if array has duplicates

OSCC · JavaScript, Array · Oct 22, 2020

Checks if there are duplicate values in a flat array.

• Use Set to get the unique values in the array.
• Use Set.prototype.size and Array.prototype.length to check if the count of the unique values is the same as elements in the original array.

const hasDuplicates = arr => new Set(arr).size !== arr.length;

hasDuplicates([0, 1, 1, 2]); // true
hasDuplicates([0, 1, 2, 3]); // false

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